Embarrassing confession: I have never used a grey card. Please don't laugh.

Hi guys
I need to get a grey card in my life somehow - I'm not a novice, I just never got around to buying one and using it - because I want to move into LF and scanning more and it will be a nightmare trying to digitally print from negs without some kind of white balance control going on.

What's the best A. way to use a grey card for the purpose of shooting and scanning, then digitally outputting, and B. grey card to get?

I'm so ashamed not to have more knowledge on this, I've only ever understood the use of grey cards in theory and not ever actually put one to use in my work.
Will it change my life ?
Do I need one ?
I am presuming Yes!

I only have ever used a grey card to help seeing the subject in terms of grey shades. Whatever EV is indicated metering the grey card will give the same shade of grey in any area of the subject with a similar reading. But seldom have I even done that. Don't feel the need to use a grey card. Just work at exposure. And if a grey card fits your scheme then go for it.

I have one, but generally only use it nowdays for meter testing and comparisons. In situations where I might use a grey card for shooting I use an incident light meter reading, which more or less amounts to the same thing as a reflective reading off a grey card.

Way back when, I would include one in a test shot on color film so that the printer had a known target for determining the filter pack for the "real" shots.

As for it's use in a hybrid process, that's OT here, but I've never seen the need, especially for b&w.

I found it useful to help me see a grey in the subject and then in the negative and print to start with, as a learning tool.
Also it is useful for a reflective ttl surface to meter off of. say with a Horseman 4x5 meter.
It can be a standard subject refective surface to help you understand the concepts.

"There are a great many things I am in doubt about at the moment, and I should consider myself favoured if you would kindly enlighten me. Signed, Doubtful, off to Canada." (BJP 1914).

I use an indecent light meter anywhere I would use a grey card. You might use out in a test shot for exposure, out would give you a good relative point to meter to, scan to, and print to. 18% grey is the same on all three.